CN113366742A

CN113366742A - Flow guide for rotating electrical machine

Info

Publication number: CN113366742A
Application number: CN202080010639.1A
Authority: CN
Inventors: A·奥登德拉; P·桑德斯; R·J·格雷
Original assignee: Cummins Generator Technologies Ltd
Current assignee: Cummins Generator Technologies Ltd
Priority date: 2019-01-30
Filing date: 2020-01-22
Publication date: 2021-09-07
Also published as: WO2020157464A1; GB201901267D0; US20220109344A1; EP3918697A1

Abstract

A deflector for deflecting an air flow in a rotating electrical machine is disclosed, the rotating electrical machine comprising a stator (8), a stator winding (10) and a housing (12). The flow director includes a sheet of material folded to form a deflection portion (42) and a connecting portion (44). The deflection portion (42) is arranged to deflect an airflow from a gap (14) between the stator and the housing towards the stator windings (10). The connecting portion includes one or more apertures (48, 52, 54, 56, 58) adjacent the deflecting portion. The holes help to reduce or avoid the coanda effect, thereby improving impingement of cooling air on the stator end windings.

Description

Flow guide for rotating electrical machine

The present invention relates to deflectors for use with rotating electrical machines, and in particular to deflectors arranged to deflect airflow to assist in cooling the electrical machine.

Rotating electrical machines, such as motors and generators, typically include a rotor mounted on a shaft and arranged to rotate inside a stator. The rotor includes a rotor core that holds rotor windings or permanent magnets. The rotor windings or permanent magnets generate a rotating magnetic field that passes through the air gap between the rotor and the stator. The stator includes a stator core that holds stator windings combined with a rotating magnetic field. The stator itself may be held within a stator frame.

When the motor is operating, current through the stator windings and/or rotor windings, as well as other factors (such as friction and windage losses), may cause the motor to heat. Thus, many electric machines, especially those of larger design, require some form of cooling. This may be achieved by providing a fan for forcing the airflow through the motor. The fan may be mounted on the rotor shaft or may be independently driven. The airflow through the motor is typically in a generally axial direction. The primary path of airflow is through the rotor/stator air gap, and through the air gap between the stator core and the stator frame.

In the known rotating electric machine, the air flow encounters the air gap when it leaves the air gap between the stator core and the stator frame. This gap is due to the presence of the end windings extending out of the stator core and this requires the stator frame to be longer than the stator core. The presence of the voids causes vortices to be introduced into the gas flow. This can result in pressure losses, reduce the airflow velocity, and result in a reduction in the amount of heat transferred to the cooling air. Furthermore, the air flow leaving the stator/frame air gap may bypass the end windings to a large extent. As a result, relatively less cooling of the end windings is possible.

In order to improve the cooling of the stator end windings, it has been proposed to provide a flow director which redirects the air flow from the stator/frame air gap towards the end windings. For example, WO2018/189523 in the name of the applicant (the subject matter of which is incorporated herein by reference) discloses a plurality of deflectors (baffles) arranged at spaced apart locations circumferentially around a motor. Each flow director includes a baffle, a connecting member, and an attachment member. The baffles present the airflow from the stator/frame air gap at an angle of about 45 deg. to direct the airflow toward the stator end windings. The connecting member is for connecting the baffle to the attachment member. The attachment member is used to attach the deflector to the frame of the motor. The connecting member extends axially inside the frame from the attachment member to position the baffle at a position facing the outlet of the stator/frame air gap.

The flow director disclosed in WO2018/189523 has been found to be effective in reducing the temperature of the stator end windings. Further, assembly and maintenance of the electric machine is facilitated by providing a plurality of baffles in spaced arrangement around the electric machine rather than a continuous annular baffle. However, a disadvantage of flow directors is that they comprise multiple parts and require various manufacturing processes, such as stamping, machining and welding. Thus, the manufacture of the deflector may be relatively complex and expensive, which may add considerable additional cost to a standard motor.

According to a first aspect of the present invention, there is provided a deflector for deflecting gas flow in a rotary electric machine, the rotary electric machine comprising a stator, a stator winding and a housing, the deflector comprising a sheet folded to form a deflecting portion and a connecting portion, wherein the deflecting portion is arranged to deflect gas flow from a gap between the stator and the housing towards the stator winding and the connecting portion comprises an aperture adjacent to the deflecting portion.

The invention may provide the advantage by providing a flow deflector comprising a sheet folded to form a deflecting portion and a connecting portion and providing the connecting portion with holes in that the manufacture of the flow deflector may be relatively simple and cost-effective while still providing a suitable redirection of the air flow.

If a folded deflector without holes is used, the airflow may have a tendency to flow along the surface of the deflector due to the coanda effect. This may reduce the effectiveness of the deflector in redirecting the airflow. Thus, the aperture may be arranged to reduce the coanda effect of the airflow over the surface of the flow director. This may help ensure that the airflow is redirected in the proper direction, such as towards the stator end windings.

Preferably, the aperture is positioned immediately behind the deflecting portion in the direction of gas flow. This may help to reduce the coanda effect and thus help to ensure proper airflow redirection. For example, the aperture may be adjacent to or overlap the fold between the deflecting portion and the connecting portion.

In one embodiment, the aperture is located near the fold between the deflection portion and the connecting portion. However, it has been found that improved results may be obtained if the aperture overlaps the fold (i.e. some or all of the material in the fold is removed). Thus, the aperture may remove at least some (and possibly all) of the fold between the deflection portion and the connection portion. For example, the folds may have fold radii and the apertures may remove some or all of the fold radii.

The length of the hole (in the direction of airflow) is preferably large enough to help reduce the coanda effect while leaving enough material to ensure that the connection has sufficient strength. For example, the length of the aperture may be at least 10% or 20% and/or less than 90% or 80% of the length of the connecting portion, although other values may be used instead.

In one embodiment, a single aperture is provided. This may allow the use of a relatively simple manufacturing process.

The width of the aperture (in a direction perpendicular to the direction of the airflow and/or tangential to the circumference of the motor) is preferably large enough to provide proper airflow redirection, while leaving enough material to ensure that the connecting portion has sufficient strength to support the deflecting portion. For example, the width of the aperture may be at least 50% of the width of the connecting portion, and preferably at least 60%, 70%, 75%, 80% or 85% of the width of the connecting portion. In another aspect, the width of the aperture may be less than 95% or less than 90% of the width of the connecting portion. Of course, it should be understood that other values may be used as appropriate depending on the situation.

In another embodiment, a plurality of holes are provided. For example, two, three or more apertures may be provided across the width of the connecting portion. The respective apertures may be positioned immediately behind the deflecting portion in the direction of gas flow and/or adjacent or overlapping the fold between the deflecting portion and the connecting portion. This may help ensure that the connecting member has sufficient strength while still providing proper airflow redirection.

Where a plurality of apertures are provided, the total amount of material removed by the apertures is preferably large enough to provide adequate airflow redirection, while leaving sufficient material to ensure that the connecting portion has sufficient strength to support the deflecting portion. For example, the sum of the widths of the apertures may be at least 50% of the width of the connecting portion, and preferably at least 60%, 70%, 75%, 80% or 85% of the width of the connecting portion.

The or each aperture may be of any suitable shape. For example, in one embodiment, the aperture is rectangular. This may allow for relatively easy formation of the hole, for example by stamping. However, the aperture may be of any other shape, for example circular, elliptical or any other closed curve, or any type of polygon, such as triangular, quadrilateral (for example trapezoidal/trapezoidal, isosceles trapezoidal or kite-shaped), pentagonal, hexagonal or a polygon with any other number of sides. The aperture may have straight and/or curved sides.

In another embodiment, a plurality of circular holes are provided across the width of the connecting portion. This may allow holes to be formed by stamping or drilling.

In a further embodiment, the width of the one or more apertures tapers inwardly in a direction away from the deflecting portion. For example, the or each hole may be triangular or trapezoidal (trapezium), the base of which extends parallel to the fold between the deflection portion and the connection portion. This may provide improved aerodynamic performance, but may be at the cost of some added complexity.

It will be appreciated that any suitable number and/or shape of apertures may be provided, as appropriate. In the case where there are two or more holes, the respective holes may be the same as or different from each other.

In the case of a hole having straight sides, the edges of the hole may extend parallel to the fold between the deflection portion and the connection portion.

The hole may be, for example, a hole punched or drilled in the deflector. The flow director may be made of any suitable material, such as metal or heat resistant plastic.

Preferably, the deflecting portion and/or the connecting portion are substantially flat. This may allow the deflector to be made of a flat sheet which may then be folded to form the deflecting portion and the connecting portion.

The deflecting portion may lie in a plane that is at an angle to the plane of the connecting portion. For example, the plane of the deflection portion may be at an angle of at least 20 ° or 30 ° and/or less than 70 ° or 60 ° to the plane of the connection portion, although other values may be used instead. Preferably, the plane of the deflecting portion is at an angle of about 45 ° to the plane of the connecting portion.

Preferably, the deflection portion is angled to the axial direction of the motor. For example, the deflecting portion may be at an angle of about 45 ° to the axial direction of the motor. Preferably, the deflecting portion is arranged to deflect the gas flow from a substantially axial direction to a direction having at least a radial component. For example, the deflecting portion may be arranged to deflect the airflow from the stator/housing air gap towards the stator end windings.

The edge at the end of the deflecting portion may be curved. This may help to accommodate the deflector inside the annular housing of the motor.

The connecting portion may be arranged to support the deflecting portion and/or to connect the deflecting portion to another component, such as a part of the deflector and/or the motor.

Preferably, the deflector further comprises an attachment portion for attaching the deflector to a housing of the motor. In this case, the connecting portion is preferably between the deflecting portion and the attaching portion.

The connecting portion may be arranged to extend from the attachment portion towards the interior of the housing so as to position the deflection portion inside the housing. For example, the connecting portion may position the deflecting portion to face the exit of the stator/housing air gap and/or radially outward toward the stator end windings. This may help to ensure proper redirection of the airflow.

The attachment portion is preferably angled with respect to the connection portion. For example, the sheet may be folded to form a transition between the connecting portion and the attachment portion. The angle between the two may be about 90 ° or some other angle.

Preferably, the attachment portion comprises at least one aperture for attaching the flow director to a housing of the motor.

In use, the attachment portion preferably extends in a substantially radial direction, the connection portion extends in a substantially axial direction, and/or the offset portion is at an angle (e.g., 45 °) to the axial direction.

The deflector may be arranged to extend through a section of the motor, i.e. the deflector may extend through part but not all of the circumference of the motor. Thus, the flow director may be arranged such that a plurality of flow directors can be provided in a spaced apart arrangement around the circumference of the motor.

According to another aspect of the present invention there is provided a rotary electric machine comprising a plurality of deflectors in any form described above.

Preferably, the motor includes:

a stator having a stator winding;

a housing; and

a fan for drawing air through the motor,

and the flow director is arranged to deflect the air flow leaving the air gap between the stator and the housing towards the stator windings.

A corresponding method may also be provided. Thus, according to another aspect of the invention, there is provided a method of deflecting gas flow in a rotating electrical machine, the electrical machine comprising a stator and a housing, the method comprising deflecting gas flow leaving an air gap between the stator and the housing towards the stator windings using a deflector, the deflector comprising a sheet folded to form a deflecting portion and a connecting portion, the connecting portion comprising an aperture adjacent to the deflecting portion. The holes may reduce the coanda effect of the airflow over the surface of the flow director.

Features of one aspect of the invention may be provided with any of the other aspects. Apparatus features may be provided with method aspects or method features may be provided with apparatus aspects.

In the present disclosure, terms such as "radial", "axial" and "circumferential" are generally defined with reference to the axis of rotation of the rotating electrical machine, unless the context indicates otherwise.

Preferred embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

fig. 1 is a radial sectional view through part of a rotary electric machine;

FIG. 2 illustrates a previously considered deflector design;

FIG. 3 illustrates another previously considered deflector design;

fig. 4 shows how a plurality of flow directors may be spaced around the circumference of the rotary electric machine;

FIG. 5 illustrates one possible deflector design;

FIG. 6 illustrates test results performed using a deflector of the type shown in FIG. 5;

FIG. 7 illustrates a deflector design in an embodiment of the present invention;

FIG. 8 illustrates test results performed using a deflector of the type shown in FIG. 7;

FIG. 9 illustrates a deflector design in another embodiment of the present invention;

fig. 10 illustrates the results of a test performed using a deflector of the type shown in fig. 9; and

fig. 11 to 13 show deflector designs in other embodiments of the invention.

Fig. 1 is a radial sectional view through a portion of a rotary electric machine. The machine comprises a rotor 2 inside a stator 4 with an air gap 5 between them. The rotor 2 is mounted on a shaft, wherein the axis of rotation is indicated by the dashed line 6. The stator 4 includes a stator core 8 having slots on an inner circumference, and stator windings wound in the slots. The stator windings extend through the slots in a substantially axial direction. The end windings 10 extend out of the stator slots and around the outside of the stator core in a substantially circumferential direction.

The stator 4 is accommodated in the stator frame 12. An engagement rod (not shown in fig. 1) is attached to the stator frame 12. The engagement rod extends through the motor in the axial direction and engages with the stator core 8 on its outer circumference in order to position the stator core within the stator frame. The engagement bars create an air gap 14 between the stator core 8 and the stator frame 12. The stator frame 12 terminates in an end plate 16.

A shaft driven fan 18 is located at the drive end of the motor to draw cooling air through the motor. This air flow passes mainly in the axial direction through the rotor/stator air gap 5 and the stator/frame air gap 14, as indicated by the arrows in fig. 1. If desired, one or more external independently driven fans or any other suitable means of forcing air through the motor may be used in place of the shaft driven fan.

Still referring to fig. 1, it can be seen that there is a gap at the exit of the air flow from the stator/frame air gap 14. This gap is due to the presence of the end windings 10, which requires the stator frame 12 to be longer than the stator core 8. It has been proposed to position baffles within this gap to deflect the airflow from the stator/frame air gap 14 towards the end windings 10. It has been found that such a flow director may help improve the cooling of the electrical machine by reducing the temperature of the end windings and/or by reducing eddy currents in the air gap, thereby improving the air flow through the electrical machine.

Fig. 2 shows a previously considered deflector design. Referring to fig. 2, the deflector 20 includes a baffle 22, a connecting member 24, and an attachment member 26. The baffle 22 is angled relative to the axis of the motor. The baffle 22 is connected to an attachment member 26 by means of a connecting member 24. The attachment member 26 includes a plurality of bolt holes 28 for connecting the deflector to the stator frame. For example, the deflector may be connected to the end plate 16 of the stator frame 12 by means of bolts passing through bolt holes 28. The flow director 20 may be, for example, as disclosed in WO 2018/189523.

Fig. 3 shows another previously considered deflector design. In this arrangement, the flow director 20 'includes a flow deflector 22', two connecting members 24 'and an attachment member 26'. The support 29 is provided to reinforce the joint between the connecting member and the attachment member. In use, bolt holes (not shown in fig. 3) are used to bolt the deflector to the stator frame in a similar manner to the arrangement of fig. 2.

Fig. 4 illustrates how a plurality of deflectors are used in the rotary electric machine. Referring to fig. 4, in this example, eight flow directors 20' are provided at spaced apart locations around the motor circumference. Adjacent deflectors are circumferentially spaced apart from each other at an angle of about 45 °. In this example, three different types of flow directors are used, each type of flow director having a different width (in the tangential direction) than the other types of flow directors. This may allow the deflector to deflect air flow from air gaps of different sizes caused by different spacing between adjacent engagement bars. However, a single type of flow director or any other number of types of flow directors may be used instead.

Providing the deflector as multiple segments in the manner shown in fig. 2-4 may allow the deflector to fit between the engagement bars in the stator/frame air gap and may facilitate manufacturing and assembly.

It has been found that flow directors such as those shown in fig. 2-4 are effective in reducing the temperature of the stator end windings and thus are effective in improving motor cooling. However, a disadvantage of such flow directors is that they comprise multiple parts and require various manufacturing processes, such as stamping, machining and welding. It has therefore been found that such a deflector is relatively expensive to manufacture and may add considerable additional cost to a standard motor.

The applicant has studied various possible alternative deflector designs in an attempt to solve the above mentioned problems.

Fig. 5 shows one possible flow director design. The flow director shown in this example is made of a single sheet that is folded into shape. The sheet material in this example is metal, but the flow director may be made of any other suitable material, such as heat resistant plastic.

Referring to fig. 5, the deflector 30 includes a deflecting portion 32, a connecting portion 34, and an attachment portion 36. The attachment portion 36 includes a plurality of bolt holes (not shown in fig. 5) for connecting the deflector to the stator frame. The connecting portion 34 serves to extend the fluid director to the inside of the stator frame. The deflecting portion 32 serves to deflect the airflow from the stator/frame air gap towards the stator end windings. The end of the deflecting portion 32 is bent to fit inside the annular stator frame.

In fig. 5, the first fold 33 forms a transition between the flow guide portion 32 and the connection portion 34. The angle between the flow guiding portion 32 and the connecting portion 34 is approximately 45. The second fold 35 forms a transition between the connecting portion 34 and the attachment portion 36. The angle between the connecting portion 34 and the attachment portion 36 is approximately 90 °. Each of the folds 38, 40 has a fold radius that is selected to provide a reasonably quick transition from one portion to the other while avoiding excessive strain in view of the characteristics of the material from which the flow director is made.

Fig. 6 illustrates the results of a test performed using a deflector of the type shown in fig. 5. Referring to fig. 6, the deflector 30 is positioned such that the deflecting portion 32 faces the airflow from the stator/frame air gap. As shown by the arrows in fig. 6, the air flow leaves the stator/frame air gap and is deflected downward. However, the airflow then returns to the substantially axial direction along the bottom surface of the connecting portion 34. Therefore, little airflow impinges on the stator end windings 10. This reduces the cooling effect of the air flow on the stator end windings.

Further studies have shown that the behavior of the airflow shown in FIG. 5 is due to the coanda effect

The result is. The coanda effect is a phenomenon in which the jet attaches itself to a nearby surface and remains attached even if the surface curves away from the original jet direction.

Fig. 7 shows a flow director design in an embodiment of the invention. The deflector of fig. 7 is made from a single sheet of material that is folded into shape in a manner similar to the deflector of fig. 5. However, the flow director of fig. 7 is modified to reduce the coanda effect. This is achieved by making holes in the connecting portion.

Referring to fig. 7, the fluid director 40 of this embodiment includes a deflecting portion 42, a connecting portion 44 and an attachment portion 46. The first fold 43 forms a transition between the flow guide portion 42 and the connecting portion 44. The second fold 45 forms a transition between the connection portion 44 and the attachment portion 46. As with the deflector of fig. 5, the attachment portion 46 is for connecting the deflector to the stator frame, the connection portion 44 is for extending the deflector inside the stator frame, and the deflection portion 42 is for deflecting the air flow entering from the stator/frame air gap towards the stator end windings.

In the deflector of fig. 7, a hole 48 is punched in the connecting portion 44 near the fold 43 between the deflector portion 42 and the connecting portion 44. Thus, in this embodiment, the hole is punched so as to preserve the folding radius of the folded portion 43. The aperture 48 is rectangular with one edge extending along an edge of the fold 43. The hole extends in the width direction (i.e. the direction tangential to the circumference of the motor) for about 80% of the width of the deflector, about 10% of the deflector material remaining on each side. The bore 48 extends in the length (axial) direction for about 30% of the length of the connection portion. It should be understood, of course, that these drawings are merely examples and can be adapted to specific situations.

Fig. 8 illustrates the results of a test performed using a deflector of the type shown in fig. 7. Referring to fig. 8, the flow director 40 is positioned such that the deflecting portion 42 faces the airflow from the stator/frame air gap 14. As indicated by the arrows in fig. 8, the air flow leaves the stator/frame air gap 14 and is deflected downwardly by the deflecting portion 42. The presence of the holes 48 reduces the coanda effect so that the air flow continues on a downward trajectory towards the stator end winding 10. Thus, the design of the flow deflector 40 improves the impingement of the air flow on the end windings 10 and thus improves the cooling of the end windings compared to the design of fig. 5.

The deflector of fig. 7 may be formed by first stamping the deflector in a flat form from a sheet of material, such as metal, then punching holes in the deflector, and then folding the deflector into the shape shown. Holes may then be drilled in the attachment portion 46 at appropriate locations to attach the deflector to the stator frame. This is a relatively simple and cost-effective process, and most of the complexity associated with producing the flow director of fig. 2-4 may be avoided. Of course, it should be understood that other materials and manufacturing processes may be used as appropriate.

Fig. 9 shows a deflector design in another embodiment of the invention. Referring to fig. 9, the deflector 50 of the present embodiment includes a deflecting portion 42, a connecting portion 44, and an attachment portion 46 similar or identical to the corresponding portions of the deflector 40 of fig. 7. However, in the embodiment of fig. 9, a hole 52 is provided, which hole 52 removes the folding radius of the fold 43 between the connecting portion 44 and the deflecting portion 42. Also shown in fig. 9 are holes 49 in the attachment portion 46, the holes 49 being used for attaching the deflector to the stator frame.

Fig. 10 illustrates the results of a test performed using a deflector of the type shown in fig. 9. Referring to fig. 10, the flow director 50 is positioned such that the deflecting portion 42 faces the airflow from the stator/frame air gap 14. As indicated by the arrows in fig. 10, the airflow exits the stator/frame air gap 14 and is deflected downwardly by the deflecting portion 42. The presence of the holes 52 reduces the coanda effect so that the air flow continues on a downward trajectory towards the stator end winding 10. The downward trajectory is more pronounced than the trajectory of fig. 8, resulting in a greater impact of the airflow on the end windings.

When comparing the heat transfer coefficients, it was found that the deflector design of fig. 9 provides better cooling efficiency than the deflector design of fig. 7. However, both designs improve cooling efficiency compared to the design of fig. 5.

Fig. 11 shows a deflector design in another embodiment of the invention. Referring to fig. 11, the fluid director of the present embodiment includes a deflecting portion 42, a connecting portion 44 and an attachment portion 46 similar or identical to the corresponding portions of the fluid director of fig. 7 and 9. However, in the embodiment of fig. 11, two holes 54 are provided in the connecting portion 44 across the width of the connecting portion (perpendicular to the direction of airflow). In this example, the two holes 54 remove the fold radius of the fold between the connecting portion 44 and the deflecting portion 42. This arrangement may be preferred in case additional strength is needed in the center of the flow director.

Fig. 12 shows a deflector design in another embodiment of the invention. Referring to fig. 12, the fluid director of the present embodiment includes a deflecting portion 42, a connecting portion 44 and an attachment portion 46 that are similar or identical to the corresponding portions of the fluid director of the previous embodiment. However, in the embodiment of FIG. 12, four circular holes 56 are stamped or drilled in the connecting portion 44 across the width of the connecting portion. It should be understood that a different number of holes may be provided. Further, a plurality of holes may be provided in the length direction (parallel to the air flow direction) as well as in the width direction.

Fig. 13 shows a deflector design in another embodiment of the invention. Referring to fig. 13, the fluid director of the present embodiment includes a deflecting portion 42, a connecting portion 44 and an attachment portion 46 that are similar or identical to the corresponding portions of the fluid director of the previous embodiment. However, in the embodiment of fig. 13, a triangular hole 58 is provided in the connecting portion 44. One edge of the triangular aperture 58 removes the fold radius of the fold between the connecting portion 44 and the deflecting portion 42. The other edges of the triangular aperture 58 taper towards each other so that the width of the aperture decreases with distance away from the fold. This may allow for a greater reduction in the coanda effect at the interface between the connecting portion 44 and the deflecting portion 42, which would otherwise be most pronounced.

Thus, in an embodiment of the invention, a flow director having a folded design is used instead of the flow director shown in fig. 2 to 4. By using a folded design, the flow director may be manufactured from a single sheet, thereby reducing material costs and simplifying the manufacturing process. One or more holes are punched or drilled in the connection portions to reduce or avoid the coanda effect and thereby improve impingement of cooling air on the stator end windings.

It is to be understood that embodiments of the invention have been described by way of example only and that changes in detail may be made within the scope of the appended claims. For example, any number of apertures may be provided across the width of the connecting member. A plurality of small circular holes may be punched or drilled in the deflector near the fold between the connecting member and the deflecting member. The or each aperture may have any suitable shape, such as circular, elliptical, triangular, trapezoidal, isosceles trapezoidal, kite-shaped, pentagonal, hexagonal or polygonal with any other number of sides. The flow director may be made of a material other than metal, such as a heat resistant plastic. The flow director may be manufactured using other techniques, such as injection molding. Other detail modifications will be apparent to persons skilled in the art.

Claims

1. A deflector for deflecting gas flow in a rotary electric machine, the rotary electric machine comprising a stator, stator windings and a housing, the deflector comprising a sheet folded to form a deflecting portion and a connecting portion, wherein the deflecting portion is arranged to deflect gas flow from a gap between the stator and the housing towards the stator windings and the connecting portion comprises an aperture adjacent to the deflecting portion.

2. The flow director of claim 1 wherein the apertures are arranged to reduce the coanda effect of airflow across the surface of the flow director.

3. The flow deflector according to claim 1 or 2, wherein the aperture is positioned immediately behind the deflecting portion in the direction of the air flow.

4. The flow deflector of any preceding claim, wherein the aperture is adjacent to or overlaps a fold between the deflecting portion and the connecting portion.

5. The flow director according to any one of the preceding claims, wherein the apertures eliminate at least some of the folds between the deflection portion and the connection portion.

6. The flow deflector according to any of the preceding claims, wherein the length of the aperture is at least 10% or 20% and/or less than 90% or 80% of the length of the connecting portion in the direction of the gas flow.

7. The flow director according to any one of the preceding claims, wherein the width of the aperture is at least 50% of the width of the connecting portion, and preferably at least 60%, 70%, 75%, 80% or 85% of the width of the connecting portion.

8. The flow director of any one of claims 1 to 6, wherein the connecting portion comprises a plurality of holes.

9. The flow director of claim 8, wherein the sum of the widths of the apertures is at least 50% of the width of the connecting portion, and preferably at least 60%, 70%, 75%, 80% or 85% of the width of the connecting portion.

10. The flow director according to any one of the preceding claims, wherein the deflecting portion and/or the connecting portion is substantially flat.

11. The flow director according to any one of the preceding claims, wherein the deflection portion lies in a plane that is at an angle to the plane of the connection portion.

12. The flow director according to any one of the preceding claims, wherein the deflection section is angled to the axial direction of the motor.

13. The flow deflector according to any one of the preceding claims, wherein the deflecting portion is arranged to deflect the gas flow from a substantially axial direction to a direction having at least a radial component.

14. The deflector according to any of the preceding claims, wherein the edge at the end of the deflecting portion is curved.

15. The deflector according to any of the preceding claims, wherein the connecting portion is arranged to support the deflecting portion and/or to connect the deflecting portion to another component.

16. The deflector according to any of the preceding claims, further comprising an attachment portion for attaching the deflector to a housing of the motor.

17. The flow director of claim 16, wherein the connecting portion is between the deflecting portion and the attachment portion.

18. The flow deflector of claim 16 or 17, wherein the connecting portion is arranged to extend from the attachment portion to the housing interior so as to position the deflecting portion within the housing interior.

19. The flow director of any one of claims 16 to 18, wherein the attachment portion is angled with respect to the connection portion.

20. The deflector of any one of claims 16-19, wherein the attachment portion comprises at least one aperture for attaching the deflector to a housing of the motor.

21. The deflector according to any of the preceding claims, wherein the deflector is arranged to extend through a section of the motor.

22. The deflector of any preceding claim, wherein the deflector is arranged such that a plurality of deflectors can be provided in a spaced arrangement around the circumference of the motor.

23. A rotating electrical machine comprising a plurality of deflectors according to any one of the preceding claims.

24. The rotating electrical machine according to claim 23, the electrical machine comprising:

a stator having a stator winding;

a housing; and

a fan for drawing air through the motor,

wherein the flow director is arranged to deflect airflow exiting an air gap between the stator and the housing towards the stator windings.

25. A method of deflecting gas flow in a rotating electrical machine, the electrical machine comprising a stator, stator windings and a housing, the method comprising deflecting gas flow exiting an air gap between the stator and the housing towards the stator windings using a flow director, the flow director comprising a sheet folded to form a deflecting portion and a connecting portion, the connecting portion comprising an aperture adjacent to the deflecting portion.